END OF YEAR9 Part 2 Flashcards
What are waves used for
To transfer energy and information
Tell me about transverse waves
They vibrate at 90° to the direction of energy transfer eg all electromagnetic waves
Tell me about longitudinal waves
They vibrate parallel to the direction of energy transfer e.g. sound waves. the vibrations are known as compressions and rarefactions
Tell me about mechanical waves
They need a medium to travel through and may be transverse or longitudinal eg waves on the slinky spring
What is the amplitude of a wave
It is the height of the wave crest from the position of rest
What is the frequency of a wave
It is the number of Wavecrest sporting a point in one second
Unit: Hertz
What is the wavelength of a wave
It is the distance from one Wavecrest to another
What is the wave equation
Speed(m/s) = frequency(Hz) X wavelength(m)
What is the normal
It is a line drawn perpendicular to the mirror
What is the angle of incidence
The angle between the incident ray and the normal
What does the angle of incidence have to equal for the Ray of light to be reflected by a plane mirror
The angle of reflection
What is a plane mirror like
The image is upright, virtual and the same size as the object
What is a real image
It can be projected onto a screen.a virtual image only exists in the mirror
What is refraction
It is the change in direction of waves when they travel across a boundary. this change in direction is due to a change in speed
What happens to the angle of refraction in the glass when light passes from air into glass
The angle of refraction is less than the angle of incidence
What is diffraction
It is the spreading out of waves when they pass through a gap or round an obstacle
The narrower the gap………….
The greater the diffraction
Does the gap have to be a similar size to the wavelength of the wave in order for the diffraction to take place
Yes. that is why light cannot diffract around an opendoor way but sound can
What happens if radio waves do you not diffract enough when they go over hills
Radio and TV reception will be poor
What is the frequency range of the normal human ear
20Hz to 20 000Hz
What are sound waves
They are vibrations that travel through a medium. they cannot travel through a vacuum
What are echoes due to
They are due to sound waves reflected from a hard smooth surface
Where does refraction take place
At the boundaries between layers of air at different temperatures. the warmer the air the greater the speed of sound
Why can you hear sound a long way away from its source at night
Because soundwaves refract back to the ground
When does the pitch of a note increase
If the frequency of the soundwave increases
When does the loudness of a note increase
If the frequency of the soundwave increases
Vibrations created in a musical instrument produce sound waves. what do you say the instrument does
Resonates
What are electromagnetic waves
They are electric and magnetic disturbances that transfer energy from one place to another
What waves can travel through a vacuum at 300 million M/S
Electromagnetic waves
What are the waves in the electromagnetic spectrum
Radio, microwaves, infrared, visible light, ultraviolet, x-ray, gamma rays
What colours does white light contain
All the colours of the visible spectrum
In a digital camera the light is focused by the lens on to a sensor consisting of thousands of tiny light sensitive cells called…….
Pixels
What is infrared used for
For carrying signals from remote handsets and in optical fibres.it is also used in infrared cameras and infrared scanners in hospitals
What are optical fibres
They are very thin transparent fibres that are used to transmit signals By light and infrared radiation. The light is totally internal reflected inside the fibre.
medical use: endoscope
What do you microwaves do
They carry mobile phone calls. further research is needed to evaluate whether or not mobile phones are safe to use
What are microwaves also used for
For satellite phone and TV links because they can pass through the atmosphere
What are radio waves used for
For Radio and TV broadcasting, radio communications and mobile phone calls. they can also be used instead of cables to connect a computer to other devices such as a printer. this is known as Bluetooth
Why are radio waves of different wavelengths used for different purposes
Because the wavelength affects how far they can go, how much they spread and how much information they can carry
What are radio waves less than 1 m used for
TV broadcasting
What are radio waves of wavelengths greater than 100 m used by
National and international radio stations
Different wavelengths of electromagnetic radiation have different……
Effects on living cells
What can some electromagnetic radiation cause
Microwaves and radio waves can cause internal heating.
infrared can cause skin burns.
UV, X and gamma rays can cause more severe cell damage
Please press here
Recent observations suggest distant galaxies are accelerating away from each other suggesting that the expansion of the universe is accelerating. the acceleration may be caused by an unknown source of energy called dark energy
